Deconstructing the Blues

Stressful life events such as the loss of a job can lead to depression, but not everyone shows this response. A study of a large group of young adults in New Zealand by Caspi et al. provides evidence that stress is more likely to cause depression in individuals who carry a particular allelic variant of the gene encoding the serotonin transporter, a protein that controls serotonin levels at brain synapses. These results reinforce the emerging view that mental illness and other complex diseases cannot always be explained by genetic or environmental factors alone, but more likely arise from an interaction between the two.